Persistent Pesticides in Fluvial Sediment and Their Relationship with Black Carbon

Abstract

The persistence of Organochlorine pesticides (OCPs) and Black Carbon (BC) was studied in sediment samples from river Yamuna, a major tributary of the Ganges (one of the largest, most populated and intensively used rivers in Asia). High levels (21.41 to 139.95 ng g-1) of sum of 20 OCPs (∑20OCPs) have been detected with β-HCH as the predominant component. ∑HCH and ∑DDT constituted ~86% of ∑20OCPs. Lindane, DDT and technical grade HCH were recently used. Toxicological studies with reference to fresh water sediment quality guidelines showed alarming levels of γ-HCH and DDT. DDD, DDE, β-HCH, α-HCH, Endrin, Heptachlor epoxide and Chlordane exceeded some of the guideline levels. High levels of BC (0.46 ± 0.23 mg g-1) constituted 1.25 to 10.56% of TOC. BC was correlated with isomers of HCH, p,p’-DDT and Methoxychlor; while TOC with ∑20OCPs, γ-HCH, Endosulfan Sulfate and Methoxychlor. PCA enabled better understanding of the relationship between various OCPs, BC and TOC. The association of BC with various OCPs indicated its importance in retention of some OCPs into fluvial sediments; exhibiting the potential to reduce their bioavailability. The study is unique to report the role of BC in persistence of OCPs in fluvial sediments.